1. Field of the Invention
The present invention relates to a wireless mesh network. More particularly, the present invention relates to the wireless mesh networks and the bottleneck effect at the gateway which restricts the network throughput, and ways to optimize network capacity.
2. Description of the Related Art
Wireless mesh networking (WMN) is a promising technology for providing a wireless backhaul network made of fixed multi-hop wireless routers. Typically, a wireless mesh network includes one or more wireless routers called gateways that connect the mesh network with the wired Internet. Each wireless router provides mobile nodes with wireless access service and work as a part of the wireless backhaul network.
For the reason that wireless routers constituting the wireless mesh networks are formed as fixed nodes with little change in topology, the wireless mesh networking technology is a cost-effective means for constructing a wireless ubiquitous infrastructure in fixed buildings, such as schools and hospitals. Network topology is an arrangement of elements of a network that are interconnected with each other via communication links.
The wireless mesh network is a multi-hop network similar to an Ad Hoc network such that Ad-Hoc routing protocols such Dynamic Source Routing (DSR) and Ad-Hoc On-demand Distance Vector (AODV) are used for the wireless mesh network.
Unlike the conventional routing algorithms using the number of hops as a routing metric, however, most of the mesh network routing algorithms exploit link quality and transmission rate as routing metrics. The reason for using link quality and transmission rate as routing metrics is because the routers of a mesh network are fixed at their initial positions and have to secure redundant wireless link quality for guaranteeing Quality of Service (QoS) while acting as access points (APs).
In an Ad-Hoc network in which nodes move frequently, the DSR and AODV protocols using on-demand algorithms are effective to improve the network throughput. However, the DSR and AODV protocols are likely to cause control packet overhead problems in the wireless mesh network, of which topology does not change. Furthermore, the conventional routing protocols are designed without consideration of the wireless mesh network characteristics in that all the network traffics are delivered to a gateway.
In order to solve these problems, certain spanning tree-based routing protocols have been proposed. In a spanning tree routing protocol, a spanning tree is created for connection to a gateway. However, these routing protocols do not specify that which router is to be an optimal gateway to optimize the network capacity.
In view of the network capacity, it is known that the network capacity of a wireless mesh network is in inversely proportional to a number of wireless routers. Also, the centralization of network traffic to the gateway causes bottleneck effects. Accordingly, the gateway has to have the ability to process more than bottleneck capacity to provide reliable service.
This means that the network cannot guarantee QoS to the traffic over the bottleneck capacity. Research is currently underway for solving the routing problem while optimizing the network through by performing scheduling and routing on entire links of the wireless mesh network.
One approach to solve the bottleneck effect is to configure several gateways for load balancing of the network under the assumption that a gateway is located at a specific location already. However, this method also does not propose how to select an optimal gateway for optimizing the network capacity.
In short, although it is known that the wireless mesh network causes bottleneck effects at the gateway, thus restricting the network throughput, the conventional wireless mesh network routing protocols have been designed without consideration on how to find an optimal gateway, thereby failing optimization of network capacity.